Pros & Cons of Glass Block Windows

Mike Matthews

Glass block windows, first developed in the early 20th century, are finding new appeal as a design element in the environmentally conscious 21st century. Once confined largely to use in foundation walls and bathrooms, designers are now utilizing glass and acrylic block for exterior walls in living and bedroom areas. They also employ the translucent building blocks as room dividers in interior walls.

credit:
Photodisc/Photodisc/Getty Images

Glass block windows provide ample lighting to home office areas.

Pro: Energy-Efficient Illumination

Glass block windows offer thermal insulation values that are similar to double-pane windows, but the cement mortar that holds them in place performs a better job of blocking air infiltration than traditional vinyl or aluminum window frames. That means that glass block windows never contribute to a drafty room. And because glass block windows can be used across a large expanse of exterior wall space, they provide ample amounts of energy-efficient daylight illumination indoors.

Con: No Natural Ventilation

Sick Building Syndrome describes a home that is so tightly sealed that unhealthy or toxic fumes cannot escape outdoors. That can be a problem when flooring is cleaned with harsh chemicals or when cabinets are refinished using foul-smelling, toxic paint strippers. And while traditional windows can open up to let fresh air into the house during temperate weather, glass blocks require homeowners to continue using their heating or air conditioning system to circulate indoor air.

Pro: Green Building Credits

Installing glass block windows helps a home qualify as a LEED-certified or Energy Star-certified building. Those certification programs confirm that a home is environmentally sustainable and energy-efficient while offering a value-added bonus: Green buildings have a resale value that's between 5 percent and 35 percent higher than comparable structures. Prospective home buyers looking at a green-certified structure that includes glass block windows can expect that their energy bills will be measurably lower than similar homes.